1. Field of the Invention
The present invention relates to an optical transmitting module, particularly relates to an optical transmitting module having a CAN type package.
2. Related Prior Art
Recently, it is requested that a terminator should be installed within an optical transmitting module or an optical transmitting sub-assembly to match an input impedance thereof to the line impedance as the transmission speed in the optical communication system which increases and reaches to giga-hertz (GHz) band. Moreover, it is generally applied for an optical active device, such as a semiconductor laser diode and a pre-amplifier, to dissipate larger power in order to operate in such high-speed signal. In order to keep quality of the output signal light, it should be required not to leak the high-speed signal into the bias circuit of the laser diode.
In the optical transmitting module or the optical transmitting sub-assembly having a CAN type package, the miniaturization of the package may be easily carried out. On the other hand, to install the terminator or other electronic devices within the CAN type package is so hard because of its small sized package. One exemplary configuration is known that a block is formed on a stem of the CAN type package, and the laser diode is mounted on the block via a substrate made of aluminum nitride (AlN), which operates as a heat sink. In addition to the laser diode disposed on the heat sink, a thin film metal resistor is also formed on the AlN substrate, and electrical connection from the resistor to the lead of the package and the semiconductor are carried out by micro-strip lines.
According to such configuration of the optical transmitting module with the CAN type package, since the termination resistor can be provided within the package as a thin film resistor, the module may operate and emit light in GHz band with quality. However, it would be quite impossible to further install an inductor for de-coupling the bias circuit of the laser diode into the CAN type-package that installs the micro-strip line.
Japanese patent published as 11-243254 has disclosed that, by inserting the inductor to the bias circuit to the laser diode for de-coupling thereof, the high-frequency performance of the optical transmitting module can be enhanced. However, it would be unknown, at least within knowledge of inventors, that the de-coupling inductor that is generally bulky is built in the CAN type package without expanding the size thereof.
Therefore, one object of the present invention is to provide an arrangement of the optical transmitting module that installs the laser diode and the de-coupling inductor therein, and shows a superior high frequency performance.